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Developer & Data

57 tools

Structured data, parsing, encoding, and developer utilities

About This Category

This is LittleOne's Developer & Data category, with 57 tools across five task clusters: JSON & structured data, parsing & validation, encode & transform, generators & ops, and formatters & markup. Each tool targets a high-frequency developer task — input goes in, result comes out, no account needed.

JSON & Structured Data

Handle JSON, CSV, and structured data tasks

Parsing & Validation

Handle parsing, matching, and validation tasks

🌐
CIDR Subnet Calculator
Parse a single IPv4 CIDR locally in your browser and compute the normalized subnet, mask, wildcard mask, network, broadcast, and usable endpoint range.
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CIDR Aggregator
Batch-aggregate IPv4 / IPv6 CIDRs, IP ranges, and single IPs locally in your browser. Auto-buckets v4/v6, merges adjacent and containing blocks into the minimum CIDR list. Supports set subtraction (A − B), 8 export formats (CIDR / range / netmask / wildcard / CSV / JSON / nginx / iptables), line-level error diagnostics, and normalization warnings. Accepts flexible delimiters including newline, comma, full-width, space, tab, and semicolon.
🧭
IPv6 Toolkit
Parse IPv6 addresses locally in your browser: canonicalize, classify, CIDR compute, equal-length subnet split, EUI-64 round-trip, and batch validation. Includes Teredo decoding and .ip6.arpa reverse DNS generation.
Cron Expression Parser
Parse cron expressions into human readable schedules to reduce timer configuration errors.
🧰
cURL Command Parser
Parse cURL commands into method, URL, headers, and body for API tooling reuse.
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HTTP Header Parser
Parse raw HTTP header text into key-value structures for debugging.
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HTTP Status Code Reference
Look up HTTP status codes with descriptions, usage scenarios, confusion pairs, and related codes
🔮
Magic Bytes Viewer
Browse magic bytes signatures for common file formats with search, category filters, and drag-and-drop file identification
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Regex Tester
Test regex patterns with match highlighting, capture groups, replace preview, and code snippets.
🚂
Regex Visualizer
Convert regex patterns into railroad diagrams with bilingual structural explanation, common presets, and SVG/PNG export
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Semver Range Checker
Check whether versions satisfy semver ranges to assist dependency upgrades.
🧩
URL Query Toolkit
Parse full URLs or raw query strings locally in your browser, preserve duplicate keys, empty values, and flag params, then rebuild the output explicitly.
🧭
User Agent Parser
Parse user agent strings and identify browser, operating system, and device details.
📊
Shannon Entropy Calculator
Calculate Shannon entropy with log₂/ln/log₁₀ bases, normalized entropy, randomness gauge, and per-character contribution breakdown
⌨️
Keyboard Event Viewer
Capture and display keyboard event properties in real time, including key, code, keyCode, modifiers, and composition events
📋
MIME Type Reference
Look up MIME types and file extensions with bidirectional search, category filters, and one-click copy
🔌
Common Ports Reference
Look up 140+ common network ports with category and protocol filters, security risk annotations, and one-click copy
📍
Geohash Converter
Convert between geohashes and coordinates locally in your browser with smart detection, precision 1-12, bbox details, neighbour cells, parent prefixes, GeoJSON/WKT output, and batch conversion.

Encode & Transform

Handle encoding, transformation, and lightweight conversion tasks

🔄
Binary Complement Calculator
Visualize sign-magnitude, ones' complement and two's complement for integers with 8/16/32/64-bit widths, dec/bin/hex I/O, step-by-step derivation, color-coded bit grid and boundary presets
🔐
Base64 Encode/Decode
Encode and decode text with standard and URL-safe Base64, including UTF-8 and Unicode support.
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CRC Calculator
CRC-8/16/32/64 Checksum Calculator with 24 algorithms, text/hex/file input
XOR / BCC Checksum Calculator
Compute XOR/BCC and Sum8/Sum16-BE/LE checksums with text/hex/Base64 input, configurable init value, byte range, step-by-step trace, verification and batch mode
🔗
LRC Checksum Calculator
Compute ISO 1155 LRC (Longitudinal Redundancy Check) with text/hex/Base64 input, step-by-step trace, verification and batch mode for Modbus ASCII and serial protocol debugging
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Base-N Encode / Decode
Convert UTF-8 text, hex, Base32, Base32hex, Base64, and Base64url locally in your browser with strict rules.
🔀
Env / INI / Properties Converter
Convert conservative .env, INI, and Java properties text locally in your browser and block unsafe mappings explicitly.
🔤
HTML Entity Reference
Search common HTML entities and copy named entities, decimal refs, hex refs, CSS escapes, and JS escapes
Timestamp Converter
Convert between Unix timestamps and dates
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Unicode Lookup
Look up code points, encodings & names for any character
📡
Morse Code Translator
Translate between text and Morse code with audio playback, signal visualization, and reference chart
🔐
Caesar / Vigenère Cipher
Caesar and Vigenère cipher encrypt/decrypt with brute-force, crib filtering, chi-squared ranking, frequency analysis, IC, Kasiski auto-crack, and Tabula Recta
🔄
ROT47 Cipher
ROT47 cipher for ASCII printable characters with 0-93 shift, self-inverse detection, brute-force attack, and ASCII frequency analysis
🔐
String Escape / Unescape
Escape & unescape strings locally for JSON, JavaScript, Java, HTML, XML, SQL, and CSV
🔗
URL Encode/Decode
Percent-encode and decode URL parameters or text with Chinese, emoji, and special character support.
🔑
HTTP Basic Auth Encoder
Client-side HTTP Basic Auth encoder and decoder with real-time Base64, Authorization header, curl, and fetch snippets — supports UTF-8 and reverse decoding
🌐
Punycode Converter
Client-side Punycode / IDN encoder and decoder with auto-direction, full-URL and email support, per-label breakdown, homograph advisory, and UTS #46 nontransitional processing

Generators & Ops

Handle generators and lightweight ops tasks

🎨
ASCII Art Generator
Convert text to ASCII art with 300+ fonts, layout controls, code comment wrapping, and one-click export
🔒
Chmod Calculator
Visually calculate Linux/Unix file permissions with setuid/setgid/sticky special bits, common presets, and 3-way octal↔symbolic↔checkbox sync
🆔
Nano ID / ULID Generator
Nano ID & ULID unified generator with 6 alphabet presets, collision probability calculator, ULID timestamp decode, UUID↔ULID conversion, Client-side computation
🤖
Robots.txt Generator
Generate robots.txt rules, sitemap declarations, and common crawler directives.
🛡️
Shield Badge Generator
Generate static badges with local preview, then copy Shields-compatible URLs, Markdown, HTML, and SVG
🗺️
Sitemap Generator
Generate XML sitemaps locally from either full URLs or same-site paths, with optional changefreq, priority, and lastmod fields, then copy or download the result.
🔑
UUID Generator
Generate UUID v4 in batch with format options
🔗
Random MAC Address Generator
Generate random MAC addresses in batch with four formats, case toggle, unicast/multicast & UAA/LAA control, custom OUI prefix, and vendor presets
🔢
Sequence Number Generator
Client-side computation batch sequence generator with Simple mode (prefix+start+step+padding+suffix), DSL templates ({n:04} {ALPHA} {ROMAN} {cn} {CN} {date:YYYY-MM-DD} {rand:6}), Date mode, 9 output formats (TXT/CSV/JSON/TSV/SQL/Markdown), BigInt big-number support, fixed-point decimals, Chinese numerals & financial uppercase, Excel column letters, Roman numerals, shuffle, presets, up to 100k rows, mobile-first UI

Formatters & Markup

Handle SQL, XML, and related formatting tasks

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Tools in this category run locally in your browser. See Privacy Policy for the full local-storage and third-party-call inventory, and Disclaimer for the as-is provision.